Combined hydroisomerization-desulfurization process



Nov. 10, 1964 M.T HART 3,156,640

COMBINED HYDROISOMERIZATION-DESULFURIZATION PROCESS Filed Sept. 8, 1961 FRESH HYDROGEN GAS r r' OLEFIN FEED J /2 REACTOR 5 2/ FURNACE WVWW |3 /V\/\/\fi\ ll 3 HYDROGEN GAS BLEED GAS/LIQUID SEPARATOR LIQUID SULFUR-CONTAINING INVENTORZ MARIUS 'T HART Wc M HIS ATTORNEY United States Patent Filed Sept. 8, 1961, Ser. No. 135,795 Claims priority, application Netherlands, Sept. 9, 1960, 255 780 12 Claims. Eel. 208-64 This invention relates to a process for the catalytic conversion of unbranched or sparsely branched olefins into hydrocarbons having branched or more highly branched carbon chains. More particularly, the invention relates to a combination process for hydroisomerization of normal olefins to isoparaffins having the same number of carbon atoms and the simultaneous hydrodesulfurization of a sulfur-containing hydrocarbon oil fraction.

Normal olefins in the gasoline boiling range have a high octane rating, particularly blending octane rating. However, their presence in motor gasoline in recent years has been increasingly undesirable because of their high sensitivity and because of their effect on air pollution. Several methods are known to convert highly sensitive normal olefins into parafiins of low sensitivity, thus, obviating the air polution problem as well. One method is to saturate the olefins by hydrogenation with a hydrogenation catalyst such as cobalt, molybdenum or aluminum.

Another method of converting normal olefins is to first hydrogenate the olefin and then isomerize the resulting normal paraflin to the isoparafiin. Another method is to convert in two stages using an isomerization catalyst in the first stage and a hydrogenation catalyst in the second.

A much more improved method of converting normal olefins into isoparafiins is by hydro-isomerization, wherein unbranched or lightly branched olefins are contacted with a special catalyst which has both isomerization and by- .drogenation activity. Such a process is described fully in copending US. application No. 39,818. A high yield of branched or more highly branched hydrocarbons are thus obtained. The conversion is carried out at an elevated temperature and pressure in the presence of hydrogen or hydrogen-containing gas.

In the hydroisomerization conversion of unbranched or sparsely branched olefins, or mixtures containing one or more of such olefins, into hydrocarbons having branched or more highly branched hydrocarbon chains very great heat effects are found to occur as a result of the exothermic nature of the reaction. The resultant great increase in the temperature promotes hydrogenative cracking which is likewise an exothermic reaction. Hence, it is difficult to carry out the process on a commercial scale in a reactor with a fixed catalyst.

The conventional method of preventing excessive temperature increases, viz., the subdivision of the catalyst into a number of separate beds connected in series, and cooling the reaction mixture between the beds (this is frequently carried out by injecting liquid reaction products or fresh liquid feed) is unattractive in the present case since the heat efiects .are so great that excessive temperature increases through the separatebeds can only be prevented by using beds having a very low height and this is hardly if at all feasible from a technical point of View.

It has been proposed to minimize conversion zone temperature rises by mixing with the fresh feed before it is contacted with the catalyst at certain portion of the product obtained in the conversion. Although in this manner, the disadvantage of excessive increases in tempera- See ture may be overcome, recycling part of the product obtained into the process is a less attractive proposition in so far that small quantities of polymerization and/ or condensation products sometimes occur in the conversion product which tend to deposit on the catalyst. As a result of these deposits the catalyst life is generally adversely affected.

It has now been found that particularly good results can be obtained by mixing the fresh feed, before it is contacted with the catalyst, with a sulfur-containing hydrocarbon oil fraction which has a lower content of olefinic components than the starting material. The drawback of undesirable temperature rises is obviated in this process by the diluting effect of the added fraction which is desulfurized simultaneously while the olefinic feed is hydroisomerized. As the hydrosulfurization process gives off relatively little heat, the admixture of sulfur-containing, low-olefinic hydrocarbon oil acts to control the temperature. Control is effected primarily by adjusting the proportion of the sulfur-containing hydrocarbon fraction in the feed to be converted.

Surprisingly, it was found, when operating in accordance with the present invention, that the catalyst retained a high activity for a very long period. Moreover, the sulfur-containing hydrocarbon fraction was completely or substantially completely desulfurized after being passed over the catalyst.

The invention therefore relates to a process for the catalytic conversion of unbranched or sparsely branched olefins into hydrocarbons having branched or more highly branched carbon chains, in which process the starting material is passed at elevated temperature and pressure and in the presence of a hydrogen-containing gas through a reaction zone together with an added hydrocarbon which has a lower content of olefinic components than the starting material, which process is characterized in that the added hydrocarbon is a sulfur-containing hydrocarbon oil fraction which is completely or substantially desulfurized while being passed through the reaction zone.

The sulfur-containing hydrocarbon oil fraction added to the starting material according to the invention should have a relatively low content of olefinic components, in order to counteract excessive temperature rises in the reactor. Nor should there be any compounds in the added sulfur-containing oil which, under the reaction conditions, might give rise to the formation of polymerization and/ or condensation products.

Any sulfur-containing hydrocarbon oil fraction will generally be suitable to effect the process according to the invention. Straight-run petroleum fractions will, for example, be 'very suitable. The boiling ranges of these fractions may vary within wide limits. Preferably, however, fractions will be used having a boiling range between 0 and 250 C., such as butane fractions, light gasoline, naphtha, kerosene and jet fuels. If desired, use may be made of mixtures of these fractions with or without a portion of the product obtained in the present process.

If the fraction selected to be admixed falls completely or substantially outside the boiling range of the starting material, it will be possible, if desired, after the latter has been passed over the catalyst, to separate the converted starting material and the desulfurized fraction from the reaction mixture by means of distillation and/ or fractional condensation. It may, however, be of advantage to select an added fraction which is completely or substantially within the boiling range of the starting material, to obtain a reaction product which may, for example, be used wholly or partly as a motor gasoline component.

The sulfur-containing hydrocarbon oil fraction .is preferably added to the starting material in such a quantity that the weight ratio of the added fraction to the fresh starting material is equal to A times the difference between the bromine number of the fresh starting material and the bromine number of the added fraction, A being a number between 0.005 and 0.1. By bromine number in the present specification and claims is meant the bromine number which is determined according to the ASTM test designated D1158. Preferably, A is a number between 0.015 and 0.05. v

The sulfur content of the sulfur containing hydrocarbon oil fraction is preferably at least 0.01% by weight and preferably not more than 0.5% by weight. Particularly suitable are fractions with a sulfur content of 0.05-0.15 by weight.

The olcfinic feed, the sulfur-containing hydrocarbon oil fraction and the hydrogen-containing gas may, for example, be mixed with each other in a relatively cold state and then (after being passed, if desired, through one or more heat exchangers) raised to the desired reaction temperature in a pipe still. This manner of heating may sometimes lead to a relatively rapid fouling of the pipe stills, this presumably being due to the relatively high content of the olefinic components of the feed.

This drawback may be obviated by heating the added fraction whether or not mixed with hydrogen-containing gas to a temperature higher than the temperature at the beginning of the reaction zone, and by then mixing with the feed and as far as necessary with hydrogen-containing gas, after which the resultant mixture is introduced into the reaction zone without deliberate further heating or cooling. The added fraction is preferably heated to a temperature which is -l00 C. higher than the temperature at the beginning of the reaction zone. The temperatures and the quantities of the various streams should, of course, be so adjusted to each other as to insure that the final mixture has the desired temperature y and may be introduced into the reaction zone without deliberate further heating or cooling.

This embodiment is based on the discovery that the sulfur-containing hydrocarbon oil fraction has a considerably higher thermal stability than the starting material. This is due to the fact that the said added fraction contains no olefins or only a relatively small content of olefins. Consequently, it may be readily heated to temperatures which are above the temperature at the beginning of the reaction zone. Also, in the present mixing, the fresh hydrocarbon or hydrocarbons to be treated cannot substantially exceed the temperature of the added fraction, while when the said fresh hydrocarbon or hydrocarbons are heated in a pipe still there may be considerably higher local temperatures.

In this embodiment the relatively cold starting material and heated sulfur-containing fraction are preferably mixed in a tube and at a short distance from the reaction zone. This minimizes the drawbacks of any slight fouling, since it is obviously much easier to clean such a tube than the complicated systems of narrow pipes such as are used in pipe stills, etc. In addition with the use of such an arrangement there is always little fouling owing to the short distance between the mixing point(s) and catalyst, so that the mixture is only for a short period subject to conditions which usually promote undesirable reactions. The flow in such a tube may be of either the laminar or of turbulent type. Turbulent flow is preferred.

In the process according to the present invention, a single catalyst bed in the reaction zone may suflice, if desired.

It should be noted that when the amount of sulfurcontaining hydrocarbon oil fraction is increased, the temperature to which the added fraction should be heated decreases. As a result, the maximum possible temperature occurring during mixing is lower, and the temperature rise during the reaction is less pronounced. But economic factors limit the increase of this amount. The added fraction may be normally heated to a temperature which is higher than the temperature at the beginning of the reaction zone, for example, in one or more heat exchangers and/ or pipe stills; in this case there is little risk of fouling since a thermally stable product is heated. In some cases no separate heating of the added fraction will be required, for example, for a fraction which is already available at the desired high temperature as a refinery stream.

It is immaterial in which order the starting material, the sulfur-containing hydrocarbon oil fraction, the fresh hydrogen-containing gas and any hydrogen-containing recycle gas are mixed.

The starting material can consist of or contain one or more olefins. Thus, suitable starting materials are mixtures of one or more other hydrocarbons and/or other compounds. The process according to the present invention is particularly suitable for treating low boiling hydrocarbon oils containing a relatively large quantity of unsaturated compounds, such as gasolines and gasoline fractions obtained in the thermal reforming and the catalytic and thermal cracking, especially the lower boiling fractions obtained from such processes.

Preferably the olefinic starting material is a light catalytically or thermally cracked gasoline having a boiling range of about -200 F. and the sulfur-containing hydrocarbon oil fraction is a suitable reformer feed stock, such as a heavy straight run naphtha.

The present process is pro-eminently suitable for treating gasolines obtained by thermal cracking in the presence of steam, or fractions thereof, as well as for treating light gasolines obtained by catalytic or thermal cracking.

A particular advantage of the present process lies in the fact that in addition to the conversion of the olefinic starting material, the sulfur-containing added fraction is completely or substantially desulfurized. In a refinery this is of great technical and economic advantage since a separate desulfurization plant may, therefore, be omitted. In this connection, preferably catalysts will be used which also have a satisfactory desulfurization effect.

The catalysts employed for the process of the invention comprise one or more sulfides of the metals of the left-hand column of group VI (chromium, molybdenum, tungsten) and/or one or more sulfides of the metals of group VIII (iron, cobalt, nickel and noble metals) of the Periodic Table of Elements, distended on an acid carrier. By an acid carrier is meant a carrier which, when absorbing butter yellow and other still weaker basic indicators, shows a color change indicating an acid medium. Particularly suitable metal sulfides are nickel sulfide and cobalt sulfide. The amount of metal sulfide applied to the acid isomerization catalyst can vary within wide limits and is generally in the range from about 0.5 to about l5% by weight and preferably about 1% to 10% by weight, based on the total catalyst. The metal sulfide can be applied to the acid isomerization catalyst, e.g., silica-alumina cracking catalyst by any suitable method known per se.

Suitable acid carriers on which the metal sulfide component is distended are, for instance, compounds of silica and alumina, such as silica-alumina cracking catalysts, compounds of silica and zirconia, compounds of boron trioxide and silica, compounds of alumina and halogen, such as alumina and fluorine, and the like.

The olefins which are present in the starting material are mainly converted under the influence of the herebefore described hydroisomerization catalysts into branched or more highly branched olefins and/ or parafiins, it being found that both compounds having the same number of carbon atoms per molecule and compounds having a different number of carbon atoms per molecule are formed from a specific olefin. The degree of saturation of the final product depends on the composition of the catalyst and the reaction conditions used.

The liquid hourly space velocity of the olefinic starting material to be hydroisomerized is generally in the range of from 0.5 to 20 liters of liquid hydrocarbons per hour per liter of catalyst (l./h.l.), although lower or higher velocities may also be used.

The olefinic starting material is converted at an elevated temperature in the range of from 100 to 500 0., preferably from 200 to 500 C., and more especially from 250 to 400 C.

The conversion is carried out in the presence of hydrogen and at elevated pressure, preferably at a total pressure not exceeding 100 atm., for instance, in the range of from to 80 atm., particularly from 20 to 60 atm. The partial hydrogen pressure may vary within wide limits and is preferably from 50 to 95% of the total pressure. Pure hydrogen need not necessarily be used since hydrogencontaining gases, such as the hydrogen-rich gases formed in reforming hydrocarbon oils, are also suitable.

The invention will now be elucidated with reference to the drawing which schematically illustrates a preferred embodiment of the invention.

Referring to the drawing, the fresh olefinic feed is supplied via line 1 and mixed with the hydrogen-containing gas supplied through line 2 and with a sulfur-containing hydrocarbon oil fraction which is supplied through line 3. It is generally preferable to heat the sulfur-containing oil to a high temperature so that after mixingthe reaction mixture is completely or substantially vaporized. The reaction mixture flows through the line 4 to the reactor. The catalytic conversion takes place in reactor 5 containing catalyst bed 6 and is attended by a slight temperature rise. The reactor effiuent flows through cooler 7 to gas/ liquid separator 8. The liquid separated from the gas is withdrawnfrom separator 8 through lines 9 and 12. Line 9 is also connected with line 3 via pump 10, thus enabling part of the product to be mixed with the sulfurcontaining hydrocarbon oil fraction which is supplied through line 3. The sulfur-containing hydrocarbon oil fraction is vaporized in furnace 11 and heated to a temperature sufficiently higher than the desired reactor inlet temperature to enable the fresh olefinic feed to be vaporized and raised to the reaction temperature. The liquid passed off through line 12 is worked up in the conventional manner for the recovery of the refined oil (for example, by further expansion in a low-pressure separator, not shown, followed by stripping and/ or distillation).

Hydrogen-containing gas leaving separator 8 is recycled through line 2, compressor 13 and furnace 11. In furnace 11, the hydrogen-containing gas is heated to a temperature which preferably is about at or above the desired reaction temperature. Fresh hydrogen containing gas is supplied through line 14. If desired, a bleed stream can be withdrawn through line 15 to avoid buildup of light hydrocarbon gases.

Example I The starting material was a fraction from a gasoline obtained by catalytic cracking, which fraction had a boiling range between 38 C. and 91 C. (A.S.T.M.). This olefinic starting material had an F-11 /z octane number of 99.2 and an F-21 /2 octane number of 85.7 and contained 62% by weight of olefins, 1% by weight of aromatics and 37% by weight of saturated compounds. The bromine number was 110. The sulfur-containing hydrocarbon oil fraction used was a straightrun naphtha from a Middle East crude oil with a boiling range of from 110 C. to 180 C. (A.S.T.M.) and a sulfur content of 520 p.p.m.

The above fractions were mixed in an amount specified below and treated according to the invention an an apparatus of the type shown in the figure.

The catalyst used was nickel sulfide distended on a silica-alumina cracking catalyst (5 parts by weight of nickel per 100 parts by weight of cracking catalyst, composition of the cracking catalyst was 13% by weight of A1 0 87% by weight of SiO This catalyst was present in the form of a single bed, viz., in a quantity of 250 ml. Feed to the reactor was supplied at a rate of 500 ml. per hour (measured in a liquid state) and consisted of 120 ml. of

light cracked fraction and 380 ml. of sulfur-containing naphtha. The naphtha had previously been heated to 385 C. in still 11. The pressure at the beginning of the reactor was 60 atm.; the temperature immediately before the catalyst bed was 340 C. and immediately thereafter 370 C. The temperature in separator S was 15 C. The liquid separating in the separator was passed off through line 12. Sufficient hydrogen-rich gas was supplied through line 2 to provide a molar ratio of hydrogen to hydrocarbons of 6/1 in the mixture entering the reactor. The temperature of the cracked fraction supplied through line 1 was 27 C. and that of the gas supplied through line 2 was 385 C. The product discharged through line 12 was distilled to a cutting point of C. The resultant fraction amounting to 20% by volume of the reaction product was practically free from olefins (bromine number l) and had an F-l-lVz octane number of 96 and an F-2- 1 /z octane number of 95, which is a considerable improvement in sensitivity when compared with the starting material. The fraction boiling above 85 C. was largely desulfurized (sulfur content 10 p.p.m.).

When a fraction was separated from the reaction prodnot at a cutting point of 100 C., 30% by volume was recovered. This fraction (bromine number l) had an F-l-lVz octane number of 91 and an F-2l= /2 octane number of 90.5. The sulfur content of the higher boiling portion was now 12 p.p.m. This higher boiling portion is a desirable reforming feed and is reformed with a catalyst comprising platinum on halogenated alumina at reforming conditions, i.e., a pressure in the range from 3-40 atm., a temperature in the range from 425550 C., Hg/ oil ratio of about 2 to 15, and a liquid hourly space velocity of from about 1-10.

I claim as my invention:

1. A combination process for the simultaneous isomerization to isoparaffins of a normal olefinic material boiling within the gasoline range and desulfurization of an added sulfur-containing hydrocarbon oil fraction which comprises contacting a mixture of said olefinic material and sulfur-containing fraction in the presence of hydrogen at elevated temperature and pressure with a catalyst comprising a solid acidic isomerization catalyst on which is deposited a sulfide of a metal selected from the group consisting of the metals in the left-hand colume of Group VI of the Periodic Table, the iron group metals of Group VIII of the Periodic Table, and mixtures thereof.

2. A'process according to claim 1 wherein the sulfurcontaining hydrocarbon oil fraction contains a portion of the product obtained in the process.

3. A process according to claim 1 wherein the weight ratio of the sulfur-containing hydrocarbon oil fraction to the olefinic material is equal to A times the difference between the bromine number of the olefinic material and the bromine number of the added fraction, A being a number between 0.005 and 0.1.

4. A process according to claim 1 wherein the olefinic material is a gasoline obtained from the cracking of highboiling hydrocarbon fractions.

5. A process according to claim 1 wherein the olefinic material is a gasoline obtained by thermal cracking a hydrocarbon oil in the presence of steam.

6. A combination process for the simultaneous isomerization to isoparaffins of a normal olefinic material boiling within the gasoline range and desulfurization of an added sulfur-containing hydrocarbon oil fraction which comprises heating the sulfur-containing hydrocarbon oil fraction to a temperature higher than the desired reaction zone inlet temperature, mixing the heated sulfur-containing oil with the olefinic material and with hydrogen, and passing the mixture without deliberate further change of temperature into a reaction zone wherein said mixture is contacted at a temperature of about 100 C. to about 500 C. and elevated pressure with a catalyst comprising a solid acidic isomerization catalyst on which is deposited a sulfide of ametal selected from the group consisting of the metals in the left-hand column of Group VI of the Periodic Table, the iron group metals of Group VIII of the Periodic Table, and mixtures thereof.

7. A combination process for the simultaneous isomerization to isoparafins of a normal olefinic material boiling within the gasoline range and desulfurization of an added sulfur-containing hydrocarbon oil fraction which comprises contacting a mixture of said olefinic material and sulfur-containing fraction in the presence of hydrogen at a temperature of about 100 C,, to about 500 C. and a pressure of about 10 atmospheres to about 100 atmospheres with a solid acidic isomerization catalyst on which is deposited a sulfide of a metal selected from the group consisting of the metals in the left-hand column of Group VI of the Periodic Table, the iron group metals of Group VIII of the Periodic Table, and mixtures thereof.

8. A combination process for the simultaneous isomerization to isoparaffins of a normal olefinic material boiling within the gasoline range and desulfurization of an added sulfur-containing hydrocarbon oil fraction which comprises contacting said olefinic material and sulfurcontaining fraction in the presence of hydrogen at a temperature of about 100 C. to about 500 C., a pressure of about 10 atmospheres to about 100 atmospheres, and a liquid hourly space velocity of from about 0.5 to about 20, with a solid acidic isomerization catalyst on which is deposited from about 0.5% to about based on the weight of the final catalyst, of a sulfide of a metal selected from the group consisting of the metals in the left-hand column of Group VI of the Periodic Table; the iron group metals of Group VIII of the Periodic Table, and mixtures thereof.

9. A combination process for the simultaneous isomerization to isoparaffins of a normal olefinic material boiling within the gasoline range and desulfurization of an added sulfur-containing hydrocarbon oil fraction which comprises contacting a mixture of said olefinic material and sulfur-containing fraction in the presence of hydrogen at a temperature of about 250 C. to about 400 C., a pressure of about 20 atmospheres to about 60 atmospheres, the hydrogen partial pressure being at least of the total pressure, and a liquid space velocity of from about 0.5 to about 20, with a catalyst comprising from about 0.5 to about 15%, based on the weight of the final catalyst, nickel sulfide supported on a silica alumina having at least by Weight silica.

10. A process according to claim 6 wherein the catalyst comprises from about 0.5-to about 15%, based on the weight of the final catalysLcobalt sulfide supported as a-silica alumina having at least 60% by Weight silica.

ll. A process in accordance with claim 1 wherein the olefinic material -is a light cracked gasoline and the sulfur-containing hydrocarbon oil is a straight-run naphtha. 12. A process in accordance with claim 11 wherein the hydroisomerized-product is distilled and a higher boiling range portion thereof is subsequently catalytically reformed.

References Cited in the file of this patent UNITED STATES PATENTS 2,905,636 Watkins et a1. Sept. 22, 1959 3,011,971 Slyn'gstad et al. Dec. 5, 1961 3,016,348 Holden Jan. 9, 1962 

1. A COMBINATION PROCESS FOR THE SIMULTANEOUS ISOMERIZATION TO ISOPARAFFINS OF A NORMAL OLEFINIC MATERIAL BOILING WITHIN THE GASOLINE RANGE AND DESULFURIZATION OF AN ADDED SULFUR-CONTAINING HYDROCARBON OIL FRACTION WHICH COMPRISES CONTACTING A MIXTURE OF SAID OLEFINIC MATERIAL AND SULFUR-CONTAINING FRACTION IN THE PRESENCE OF HYDROGEN AT ELEVATED TEMPERATURE AND PRESSURE WITH A CATALYST COMPRISING A SOLID ACIDIC AND PRESSURE WITH A CATALYST COMPRISING A SOLID ACIDIC ISOMERIZATION CATALYST ON WHICH IS DEPOSITED A SULFICE OF A METAL SELECTED FROM THE GROUP CONSISTING OF THE METALS IN THE LEFT-HAND COLUME OF GROUP VI OF THE PERIODIC TABLE, THE IRON GROUP METALS OF GROUP VIII OF THE PERIODIC TABLE, AND MIXTURES THEREOF. 